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When a slipping or noisy gear brings your CNC router, robotic arm, or automation rig to a halt, the root cause is almost always a mismatch between gear quality and application demand. Makers, machine builders, and small-batch manufacturers who need a drop-in helical pinion that runs quietly under load will find this 45# steel helical gear series a dependable solution.
Each gear is machined from 45# medium-carbon steel and finished with a blackening treatment for corrosion resistance. The series covers Module 1 with tooth counts from 12 to 25 teeth and bore diameters ranging from 4 mm to 19 mm (approximately 0.16 in to 0.75 in), including plain round bores, nut-retention bores (M3–M5), D-flat bores, and keyed bores with standard keyways (3×1.4 mm, 4×1.8 mm, 5×2.3 mm, 6×2.8 mm). Both left-spiral and right-spiral hand options are available.
Typical use cases include helical gear rack-and-pinion drives for CNC gantry systems, motor output shaft pinions for 3D printer extruder drives, and reduction stage gears in small robotic joint actuators — all applications where low noise and smooth torque transmission are critical.
Machined from 45# steel for a balance of machinability and mechanical strength, suitable for moderate-load power transmission in CNC, robotics, and automation equipment.
Chemical blackening provides a uniform dark oxide layer that reduces surface corrosion and light reflection — useful in precision optical or cleanroom-adjacent environments.
Both left-hand and right-hand helix directions are stocked, allowing correct pairing for parallel-shaft helical gear sets that require opposite-hand mates.
Plain round bores (4–19 mm), D-flat bores, nut-retention bores (M3–M5), and keyed bores with 3×1.4 mm, 4×1.8 mm, 5×2.3 mm, and 6×2.8 mm keyways cover most motor shaft standards.
A broad tooth-count selection (12, 13, 15, 16, 18, 20, 24, 25 teeth) lets you dial in the gear ratio you need without custom machining.
Mod 1 is one of the most common metric gear standards, ensuring straightforward sourcing of mating gears, racks, and replacement parts from multiple suppliers.
| Module | 1 (Mod 1) |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Surface Treatment | Chemical Blackening |
| Tooth Count Options | 12, 13, 15, 16, 18, 20, 24, 25 Teeth |
| Spiral Direction | Left Spiral / Right Spiral (select variant) |
| Bore Type Options | Plain Round, D-Flat, Nut (M3/M4/M5), Keyed |
| Bore Diameter Range | 4 mm – 19 mm (approx. 0.16 in – 0.75 in) |
| Keyway Sizes Available | 3×1.4 mm, 4×1.8 mm, 5×2.3 mm, 6×2.8 mm |
| Pressure Angle | See variant options |
| Helix Angle | See variant options |
| Face Width | See variant options |
| Outside Diameter | See variant options |
| Weight | See variant options |
The tooth count determines your gear ratio. Divide the driven gear's tooth count by the driving pinion's tooth count to get the ratio. For example, a 20-tooth pinion driving a 40-tooth gear gives a 2:1 reduction. Select a tooth count that achieves your target ratio while keeping the pinion outside diameter compatible with your shaft center distance.
Helical gears must be paired with a mating gear of the opposite hand on parallel shafts. If your existing mating gear is left-spiral, select a right-spiral pinion, and vice versa. If you are building a new gear set from scratch, either hand works — just keep both gears consistent as a matched pair.
45# steel offers a tensile strength typically in the range of 600–800 MPa after standard heat treatment, making it suitable for moderate-load power transmission. For high-shock or continuous heavy-duty applications, consider gears made from alloy steel or with additional surface hardening. Contact us to confirm load ratings for your specific configuration.
Chemical blackening creates a thin iron oxide layer that offers mild corrosion resistance in dry or lightly humid indoor environments. It is not a substitute for galvanizing or stainless steel in wet or outdoor conditions. Applying a light machine oil after installation will extend the finish life.
Choose a plain round bore if you plan to secure the gear with a set screw or adhesive. Select a D-flat bore for a flat-shaft motor (common on small DC gearmotors). Choose a nut bore (M3/M4/M5) if your shaft uses a threaded end. Select a keyed bore if your shaft has a standard keyway — match the keyway dimensions (e.g., 3×1.4 mm) to your shaft specification.
Yes. All gears in this series are Module 1 (Mod 1) standard, so they mesh correctly with any Mod 1 helical rack or gear of the same helix angle and opposite hand. Verify that the mating component is also Mod 1 before ordering — mixing modules will result in incorrect meshing and rapid wear.
Yes. For a parallel-shaft helical gear drive, order one left-spiral and one right-spiral gear with the same tooth count and module. They will mesh correctly and provide the smooth, quiet operation characteristic of helical gears compared to spur gears.
